If you're letting your ducks free range, they're going to eat worms, bugs, snakes, frogs, spiders and grass more than the food you leave for them. And that's not such a bad thing, much cheaper! Fresh water is the key to always have available. As far as treats, there's a thread here that was just added a few days ago. There are tons of things you can give as treats. Here are just a few of the treats we give - dried meal worms come in first place. Probably their favorite. Peas are another; watermelon and other gourds cut open so they can get to the yummy insides. Koi fish food tossed in their pool / pond is another great treat. That's the few we rely on, but certainly not the extent of all the treats suitable for ducks.